Wednesday, July 11, 2012

The Higgs

Yup, I guess it's time to comment on the Higgs. A few physics trivia in no particular narrative or point behind it.

I guess it all started with QED. Quantum Electrodynamics. Talk to Richard Feynman and Julian Schwinger about all that. Well, not now, they're dead.

Schwinger took first crack at it, and figured it out, but the maths were exceedingly byzantine. Feynman, after a few stumbles, came up with the elegant Feynman diagrams still used today. The problem with a description of even just a simple electron, as, for example, described in Dirac's equation is a bit more messy and filled with infinities than is usually described in the media. Small wonder. It can't be reduced to a thirty second description. As Feynman put it, when pressed, "If I could describe it in thirty seconds or less, it wouldn't be worth a Nobel prize..."

Here's my favorite. Think of a electron as a dot on a computer screen. All the charge is in one central pixel. You and I want to get a better look at it, so I increase the resolution and zoom in by hundredfold, so that the one pixel showing the electron is now one hundred pixels - a ten by ten square.

Now, the electron's charge is... one central pixel. And surrounding it is ninety-nine pixels in a whirlpool of positive and negative virtual charges that pop into and out of existence. Okay, fine, zoom in another hundredfold.

Now, the charge of the electron is... sonofabitch, one pixel. And surrounding that is an even more detailed and complicated whirlpool of positive and negative charges.

Want to do it again? Because I think you know where this is going. Each magnification shows that crummy little electron as a single point charge in the middle of the screen, with an increasingly huge peacock tail of virtual particles surrounding it.

QED has an infinity problem, which Schwinger and Feynman resolved by rewriting the equations to basically cancel the infinity part out. Cheating? No, it just looks that way.

So, success! The electromagnetic force, with its accompanying boson (the particle carrying the electromagnetic force, called a photon) is successfully described mathematically, and, even better, produces an answer, when you chug through the equations, that matches reality.

Okay, now what? It's 1950, and Abdus Salam starts working on a quantum mechanical description of the strong and weak atomic forces. How well does he do? Well, he does okay. He doesn't quite get all the way, but, with the help of John Ward, they start to construct a theory of the weak nuclear force.

What is the weak force? (This is kind of important, because this is where the Higgs comes in). What is the weak force?

I don't know. But I can tell you what it does. The weak force is responsible for radioactive decay and radioactivity. It basically is what causes one nucleus to transmute into another one (usually, but not always downhill). When a neutron decays into a proton (spitting out an electron and a neutrino), that's the weak force in action. The weak force essentially transmits charge (electric) from one particle to another - turning one nucleon into another.

Take fusion in the sun, the strong nuclear force (not gonna cover it) squeezes four protons together, and the weak force converts two of the protons into neutrons, the four hydrogen atoms are transmuted into a helium. But the weak force is so feeble, that this does not always occur - so much so that, even after some 5 billion years, only half the hydrogen fuel in the solar core has been burned.

Well, Salam and Ward, Feynman (get used to him) and Murray Gell-Mann, and eventually Shelly Glashow, and Steve Weinberg figured out the maths for this force description looked a lot like what had been done for QED, but a little more complicated. (Basically, the hope was that the photon could be used as a weak force carrier, but, oh dear, the maths suggested a triplet was at work).

So, they end up around 1964 or so, through various papers and arguments (and not a few physicists grabbing microphones in tears at conferences blubbering and sobbing "I thought of it first, I just didn't publish in time. Honest, I did!"), that the triple boson threat for the weak force consisted of two massive particles W+ and W-, and a massless boson dubbed Z0. (Z0 is also referred to as "heavy light" since it is the weak force counterpart to the photon - clever, huh?)

So, now we are at a point where people are asking what they hey? Why all these bosons? And the answer increasingly seems to be: broken symmetry. When the universe was younger and hotter (temperature-wise), the weak and electromagnetic force where balanced and equal, and there was an underlying symmetry between the W, the Z, and the photon, which were at the time all massless. But as things cooled down, the symmetry broke, and suddenly the W gained mass, but the Z and photon did not. This symmetry breaking, this W boson gaining a mass as the universe cooled down is where Higgs steps in.

And actually not. Back in the 1960s, when this was all being worked out, there were six physicists each with one piece of the puzzle, called the "Gang of Six" - Francois Englert, Robert Brout, Tom Kibble, Gerald Guralnik, Carl (dick) Hagen, and Peter Higgs. All worked on what it now called The Mechanism as to how the symmetry got broken, but it was Higgs who published a paper concerning the boson.

So that's the big deal. If you look around today, you don't see Higgs bosons. They existed in a younger, hotter universe, which is you need to use the LHC to see them. And all sorts of nonsense has been written up in the media about what it all means. Does Higgs give us a theory of everything? Fuck no!

Theory suggest it gives mass to hadrons, which are all the particles that make up the visible matter in the universe - some 4% of the total mass of the universe. But that other 96% of matter we can't see? The so-called dark matter. Well, no one has a clue. Not Standard Model theorists. Not string theorists. So, there you go.

Of course, the interesting thing is, the LHC is just at the beginning of its working life, so its probably got some empirical discoveries to go through.

Of course, what I'm more interested in is... industrial nucleonics! Particle accelerators have yet to demonstrate their real tool usage to us? What do I mean by this? Well, take the laser. When it was first developed, everyone could think of obvious hillbilly uses for it like burnin' shit and blowin' shit up. But, lasers to read CDs and DVDs? Lasers used to cool matter down to a near Absolute Zero? Lasers that might be tractor beams, or for quantum computers? Get the idea?

Particle accelerators, despite the fact they are being used for cutting-edge physics, are probably still only used for the hillbilly phase. True, they are used in medical imaging and cancer therapy, materials investigation, to produce isotopes, probably to be used for nuclear reactors and maybe fusion, but that's all the obvious stuff.

For a while now, there is talk of table-top sized accelerators, and a group at Sandia has produced a neutron bran generator on a chip. Why just this past week, Los Alamos produced the most powerful neutron beam on the planet. Okay, cool! Do something cool with it! Something new. Something not thought of before. Like, I don't know, figure out how to manipulate with a Tesla sized magnetic field to produce a fusion engine. Or create a supercooled neutron laser, a matter laser, that can maybe manipulate a Bose-Einstein into hitherto unknown regimes of energy and space and time. Or perhaps create collapsium. Or a figure out a way to manipulate the weak nuclear force, or, oops, tap into the vacuum energy, like whoever it was that did it the last time, some 13. 7 billion years ago.

4 comments:

Interesting point about 'hillbilly' type applications coming first. Long time passed in applied chemistry between medieval pipe bombs and sophisticated applications like ... well, is lycra hillbilly or not, I'm confused?

I don't know whether it holds water, though. Holography was real early on the menu of laser 'applications.' (An application is something you can sell; an 'application' is something mentioned in the 'applications' paragraph of a journal paper.)

My understanding was the concept of holography came out of the field of xray and electron microscopy - predating lasers. I guess we should take cross-pollination into account. Actually, thinking more about it, I'm starting to think that the future of particle accelerators lies in the region of the ultracold. Magneto-optical traps, superconducting solenoids, ultra-pure vacuums, Tesla-strength magnetic fields, and all fed by accelerators with whatever flavor of particle or ion you wish. That's where the fun applications will come from, I'll betcha!

It occurred to me the other night (and I wasn't even stoned) that one should be able to get neutrons to pair up like Cooper pair electrons in a superchilled environment, and get a BCS-BEC (Bardeen Cooper Schrieffer) - (Bose Einstein Condensate) crossover, kind of a paired superconducting neutrons, a lased di-neutron beam, and sure enough, you can do it. Dig that!

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The term "random walk" is attributed to Karl Pearson, through a 1905 letter exchange in the journal Nature. It describes the path of a hypothetical drunkard. Since I hardly ever drink, I suppose that description fits me as well as any other. Other than that, I'm a well-muscled, good-looking, middle-aged, no-nonsense Northern Barbarian type that would just as soon put you to work as say "Hello" to you. So, Hello there! Now get back to work!